Torque-measuring wrench



Sept. 26, 1939. H. w. ZIMMERMAN 2,174,356

TonQUE-MEASUMNG WRENGH A2 sheets-sheet 1 Filed April l2, 1937 26, '1939 H. w. ZIMMERMAN ,2,174,356

ronQus-umsunme warmen Filed April 12. 1937 2 Sheets-Sheet 2 ,Z e, Z

Patent-ed sept. 26, i939 I' y 2,174,356 l `NITED STATES PATENT OFFlCE.

2,174,356 TORQUE-MEASURING WRENCH Herman W. Zimmerman, Highland Park, Ill., as-

signor, by mesne assignments, to Frederick G. Wacker and Grace J. Wacker, Lake Forest, Ill.

Application April 12, 1937, Serial No. 136,309 11 Claims. (Cl. 265-1) My invention relates to wrenches, and it has This member I5 is of part-circular shape and to do more particularly with a wrench adapted it is constructed and arranged to provide opposed for measuring the force or torque applied there- Stub-arm elements I6 and I1 located on the through in tightening, loosening or moving bolts, opposite sides of the rock center of the member 5 nuts, studs and other devices which may be gen- I5. The forward faces of the arm elements I5, I1 5 erally termed the work. are rounded for a purpose which will be referred One of the objects of my invention is to proto more particularly hereinafter. .The member vide an improved wrench of the foregoing char- I5 is rockably supported in the space I2 in the acter which is of simple and sturdy construction, following manner. The bodyQeXtenSions I3 and l is inexpensive to manufacture, andrwhich accu- Il are provided With aligned. threaded Openings 10 rately performs its torque measuring function I8, in each of which is received a similar threaded at all times. 4 bushing I9. Each bushing is provided at its outer Another object is `to provide a torque measurend with a head 20 which, when the bushing is ing wrench constructed and arranged for elecfully screwed into the respective member I3, Il,

l trically measuring 'the forcel or torque applied seats upon the outer face of the respective mem- 15 through the wrench to the work. ber I3, Il. ,The inner ends of the bushings are- A more specinc object is to provide an electric provided with unthreaded annular guide tongues torque measuring wrench in which one or more 2l which snugly engage in the aligned annular carbon resistance stacks (rheostats) are emgrooves 22 in the opposite faces of the rock memployed as force transmitting parts, the arrangeber I5, thereby rotatably securing the rock mem- 20 ment being such that an electric current is passed ber I5 within the space I2. The bushings I9 are through the carbon resistance stacks and the locked against rotation in their fully assembled current passing therethrough is measured in positions by Set SCleWS 23 engaging Suitable terms of pressure applied to the work through threaded openings in the body I0 and so located 25 such stacks. f that their head portions seat within the notches 25 Other objects and advantages become apparent formed .in the peripheral edge portions of the as this description progresses, and by reference bushings. to the drawings wherein,- ,The rock member I5- is further provided, at its Figure 1 is a top plan view, partially in horirock center, with a rectangular (or other irreguzontal section, of one form of wrench device emlarly shaped) opening 24 in which a similarly- 30 bodying my invention; shaped adapter element 25 is 'non-rotatably re- Fig. 2 is a fragmentary side elevational view, oeived. The element 25 is long enough to project kpartially in vertical section, of the structure downwardly through and beyond the bushing I9, shown in Fig. 1; where it receives a socket 26 or other suitable Fig. 3 is a wiring diagram illustrating one type adapter device for engagement with the work. 85 of electrical circuit employedin the wrench struc- The socket 26 is frictionally retained on the ture shown in Figs. l and 2; adapter element 25 by a spring and ball unit 21 Fig. 4 is a top plan View of another form of of well-known construction. The adapter ele- Wrench structure embodying my invention; ment 25 is securely locked to the rock member 4o Fig. 5 is a horizontal section taken through I5, for rotation there th, by a set /screw 28 40A the forward part of the structure shown in Fig. which engages the inner threaded portion of an ll; -and opening 29 formed in the forward end Wall of Fig. 6 is a wiring diagram illustrating one type such rock member. Small passages 30 lead from of electrical circuit employed in the structure opening 29 into the bottoms of grooves 22 and, shown in Figs. 4 and 5. by inserting a lubricant within the opening 29,' 45 The structure shown in Figs. 1 to 3, inclusive, the grooves 22 are lubricated, providing a lubriinoludes an elongated body IB to which a rearcated bearing between the bushings I9 and the wardly extending handle II is secured in any demember I5. sired manner.' The forward end portion of the It is highly desirable, in devices of this characbody I0 is bifurcate, providing a horizontal, latter, that the force or torque measuring means be 50 erally extending space I2 which is open at its of such nature as to accurately indicate at al1 sides and forward end and which is dened by a times, under all weather conditions, and after .pair of vertically-spaced, plate-like body extenlong periods of use, the force or torque applied sions I3, I4. A o therethrough to the work. My invention provides A .I'Oek member I5 is mo ted in the spate l2, electrical means for accomplishing this purpose. 55

Specifically, the body I (Fig. 1) is provided with a pair of laterally disposed, longitudinally-extending chambers 3| and 32 which are aligned with arm elements I6 and I1, and in which there are mounted piston-like pressure members 33 and 34, respectively. The pressure members 33, 34 are provided with reduced stems 35, 36 which pass through suitable openings into the space I2, and they are of such length that when the pressure members 33'and 34 are seated against the forward endsy of the chambers 3| and 32 the outer ends of the plungers engage the curved faces of the arm elements i6 and I1 and hold the rock member @5 in a central, balanced position. Carbon resistance stacks or piles (rheostats) 31 and 31a are mounted in the chambers 3l and 32, respectively, rearwardly of the pressure members 33, 34 therein. The elements 31, 31n may take any suitable and well-known form, including brass discs 38 at the opposite ends of each element yand a plurality of carbon discs or plates 39 disposed therebetween. Suitable insulation is provided around the elements 31 and 31a, insulating the same from the pressure members 33, 34 and from the body i6. Access to the chambers 3|, 32 may be provided for in any desired manner; as, for example, by providing a suitable cover plate (not shown) for the upper or lower part of the body I0, which, when removed, Will expose the chambers 3| and 32 for insertion or removal of the carbon elements.

The carbon elements 31 and 31a, as will be well understood, are of such a character that the resistance to flow of electrical current therethrough is decreased proportionately to the amount of pressure exerted on the carbon element. It will be seen in the structure so far described that, with the rock member I5 secured to the work through the socket 26, and when the Wrench is being rotated by grasping the handle |I, the force required to move the work is applied from the operator through the handle I I, through the body I0, through the carbon elements 31 and 31, through. the plunger devices 35, 36 and rock member I5. In this way, pressure is exerted upon the carbon elements 31, 31' and, as this pressure is increased, by theadded resistance to turning movement offered by the Work, the pressure is increased upon the elements 31, 31B, reducing the resistance to ow of current therethrough. The current used in the particular form of my invention shown in Fig. 1 is supplied by a storage battery 40 mounted in a battery chamber 4| formed in the rear portion of the body. The battery is coniined within the chamber 4I by a removable closure member 42, and it is urged into engagement with the mem- .berl42 by a spring 43 for proper electrical contact.

In this form of my invention, the current passing through the carbon elements 31, 31a from the battery 40 under the various pressure conditions is measured by an ammeter 44 which is of ordinary construction and which is adapted to function in the usual manner of devices of this character. The ammeter 44 includes, an indicating hand 45 which is movable in opposite directions along a scale 46 which is calibrated to register the current passing through the carbon elements 31 in terms of inch-pounds pressure applied through the wrench to the work.

It is desirable in a device ofthis character, in order to minimize unnecessary lowering of l battery potential, to provide a circuit closing arrangement which is of a more or less automatic on the inner or rear face of the rock member I5. The wall 49 bounding the rear end of space I2 is provided with a recess 50 in the opposite side walls of which there are mounted electrical contacts 5| and 52 suitably insulated from the body In. When the rock member I5 is in its central or balanced position, the switch element 41 is in a neutral position out of engagement with both of the contacts 5I and 52. However, when the wrench is applied to the work, and the work offers suiicient' resistance to turning movement to result in compression of the then-active carbon element and, in turn, relative rock movement between the rock member I5 and the body Il), the switch element engages one of the contacts 5I and 52 and closes the electrical circuit; and when this happens the ammeter hand 45 is moved in the usual manner under the control of the current passing through the structure, thereby registering the pressure applied in terms of inch-pounds.

To facilitate description of the electrical connections between the various parts, reference is made to the wiring diagram of Fig. 3.. Here it will be seen that the circuit employed is of a character well adapted for the use of an ammeter as an indicator. The ammeter 44 is provided with three terminals 60, 6I and 62. The ammeter terminal 62 insulated wire 63 to the carbon element 31, which is disposed in the chamber 3|. The ammeter terminal 60 isconnected to the other carbon element 31a which is located in the chamber 32 by a suitably insulated Wire 64. The ammeter terminal 6| is connected by a suitably insulated wire 65 to the battery 40 which is, in turn, connected through a suitably insulated wiring 66 and suitable ground connections (not shown) to the switch element 41, The contact 62 is connected through suitably insulated wiring 61 to the carbon element 31 in the chamber 3| and the other switch element 5| is connected through suitably insulated wiring 68 to the other carbon element 31a.

In the use of the foregoing structure, the adapter member 26 is applied to the work and the handle II 'is moved in a clockwise` direction (as viewed in Fig. l) to tighten the work. As the work is tightened, relative rocking movement between the member I5 and body I0 is opposed by the pressure member 33 and the carbon pile 31 upon which it acts. The carbon element is, normally, subject to some compression, at least sufficiently to permit rocking movement of the member I5 to engage the switch element 41 with the contact 52 to complete or close the circuit through vthe battery 40, wire 66, switch elements 41, 52,

wire 61, carbon pile 31, wire 63, ammeter 44 and wire 65 (Fig. 3). As soon as this circuit is closed, the .ammeter Vhand 45 is moved clockwise (as viewed in.Fig. 1) to a certain position along the scale 46, indicating in terms of current iiow the amount of pressure that is beingdapplled to the Work at that time. As the nut is further tightened, the pressure exerted on the pressure member 33 and' carbon pile 31 is increased, lowering the resistance of the carbon.- pile so that the ammeter hand 45 moves clockwise to a greater extent, indicating increased inch-pounds pressure applied to the work. 'When the wrench is 75 a counterclockwise direction, the rock member I5 acts upon the pressure member 34 to compress the carbon element 31 and, in turn, make contact between the switch element 41 and con` tact 5|, at which time the circuit is closed through the battery 40, wire 66, switch elements 41 and 5|, wire 68, carbon pile 31a, wire 64, ammeter 44, and wire 65. As this circuit is completed, the ammeter hand 45 is moved in a counterclockwise direction (as viewed in Fig. 1) to an extent dependent upon the amount of pressure exerted upon the then-active carbon pile 31.

In certain cases, I may employ a single carbon pile or resistance stack instead of the two stacks shown in Figs. 1 to 3, inclusive. Such an arrangement is shown in Figs. 4 to 6, inclusive, and will now be described. I'his structure includes 'a body 18 having a handle 1| secured to its rear end and also having a yspacev12A at its forward end similar to the space I2 of Fig. 1, except that it is elongated for a. purpose which `will become obvious. A rock member 13 `is mounted in the space 12 in a manner similar to the mounting of the rock member |5-(Figs. 2 and 5). The rock member 13 is provided with elongated arms 14 and 15 extending rearwardly in a longitudinal direction along the sides of the space 12 and having rounded end portions adapted to engage the outer ends of stems 16 and 11 of pressure members 18 y'and 18 mounted in a lateral chamber 86 in the body 18 between the rock member arms 14 and 15. A carbon resistance pile or stack 8| is mounted in the chamber 88, and this carbon pile functions similarlyto the previously-described carbon piles 31 and 31". This single carbon` pile 8| is acted upon by the rock member 13 when the wrench is moved to both tighten and loosen the work.

In this form the electric supply and indicating means includes a millivoltmeter 82 supported by the upper portion of the body 18. This voltmeter is provided with a hand 83 movable with respect to a scale 84 to an extent dependent upon the amount of current passing through the carbon pile 8|. The scale 84 is lcalibrated to register current in terms of inch-pounds pressure applied to the work through the wrench. I also employ a battery 85 mounted in a lateral',chamber 86 in the rear portion of the body 18, which chamber is closed by a removable cover 81 against which the battery 85 is yieldably pressed by spring 88 to insure proper electrical contact between the body and the battery terminal (not shown). I also employ a switch mechanism similar to that previously described, and which includes a switch element 88 carried by the rear portion of the rock member- 13 and projecting forwardly into a recess88 formed in the forward part of the body 18 at the rear end of the space 12. In the opposite sides-of the recess there are insulated contacts 8| and 82, which are engaged by the switch element 88 under the same conditions that the 'previously-described switch element 41 engages the contacts 5| and 52, i

`In this form of my invention (Figs. 4 to 6, inclusive), the switch structure 88-92, the carbon pile 8|, the battery 85 and the voltmeter 82 are connected in a Wheatstone bridge circuit, the characteri'stics'of which will be well understood,V by those skilled in the art. In the use of this circuit, any tendency toward inaccuracy due to difference of battery potential is eliminated and, even though the'power, soto speak, of the battery is reduced, an accurate pressure indicanon wm be given by the voltmeter s2 by the movement of its hand 83 in response to current vaiations caused by varying pressure applied through the carbon pile 8| to the work. To facile itate the description of this form of my invention, reference is made to the wiring diagram shown in Fig. 6, which illustrates the several parts electrically connected together in a Wheatstone bridge type of circuit. lIt will be seen, by reference to Figs. 4 to 6, that when the wrench is applied to the work and moved in a clockwise direction (as viewed in Figs. 4 Aand 5), the switch element 88 is engaged with the contact 8| as soon as the work offers a resistance requiring the application of a force sufiicient to compress the carbon pile 8| to rock movement of the member 13 to effect the contact referred to. When this contact is'made, the circuit is completed through the battery 85, switch elements 88 and 8|, and voltmeter 82,- causing the hand 83 of the voltmeter to move to a predetermined extent as determined by the amount of current passing through the carbon resistance stack or pile 8|. The voltmeter registers this current in terms of inch-pounds pressure, as above stated. When the wrench is moved in the opposite direction and the switch an extent to permit the element 88 contacts the switch contactA 82, the

circuit through the parts above mentioned is also closed and a similar indicating result takes place. In both of these instances, the current flow is such that the hand 83 of the voltmeter moves in clockwise direction (as viewed in Fig. 4). Other than above mentioned, the operation of this Aform of device is the same asthat previously described.

It is believed that the operation advantages of my invention will be well understood from the foregoing. A wrench embodying the foregoing features is adapted to accurately measure the force or torque applied through the wrench to the work, notwithstanding variable weather or other operating conditions. In the use of my invention, nuts, bolts, studs and other kinds of work may be loosened,.tightened or moved to any predetermined extent Without the necessity of using skilled labor. Distortion and breakage of such fastening devlcesfare avoided, and their life of usefulness is greatly increased.Y A wrench embodying this invention is quite' useful in setting up a series of bolts, studs and the like, particularly where such devices must all be set up, essentially. in a uniform manner.

It will be understood that although I have shown two forms of structure embodying my invention, other changes in details and arrangementsof parts may be resorted to without departing from the spirit and s cope of my invention as defined by the claims that follow.

I claim:

1. In a torque measuring wrench, a member having provision for operatively engaging the work, a second member rotatably connected to said first member, electrical means disposed between said two members and controlled by the force or torque applied to said first member.

5 being such that the force or torque is applied to the work through said members and said resistance means, said resistance means including a carbon resistance stack through which the force ortorque is applied to the work, means for supplying an electric current to'and through said stack, switch means operable by relative rock movement between said members for cutting in and out said supply means and indicating means registering the current passing through said stack in terms of pressure applied to said stack in tightening, loosening or moving the work.

3. In a torque measuring wrench, a rock member having provision for engaging the work, a support member upon which said rock member rocks, an electrical resistance means between and opposing relative rock movement of said mem= bers, said means being of a character adapted to offer a variable resistance as pressure exerted thereon is varied, means for supplying electric current to and throughsaid resistance means, means controlled by relative rock movement between said members for closing the electric circuit through said resistance means, and indicating means registering the ow 'of current through said resistance means in terms of pressure exerted to tighten, loosen or otherwise move the work.

4. In a torque measuring wrench, a rock member having provision for engaging the work, a support member uponwhich said rock member rocks, a carbon resistance means between and opposing relative rock movement of said members, an electric circuit in whichsaid carbon resistance means is disposed and in which is located a current supply means, and switch elements carried by said members for closing said circuit upon predetermined relative rock movement between said members, an electric current registering means in said circuit having a calibrated dial member and an indicator element movable relative thereto for registering current passing" through said carbon resistance means in terms of pressure applied through the carbon resistance means to the Work.

5. A torque measuring wrench comprising a body member, a member rockably supported by said body member and having provision for operative connection with the work, said rock member having opposed arm elements on 'the opposite sides of the rock center thereof, electrical resistance means disposed between said arm elements and said body member and opposing relative rock movement of said members, said electrical resistance means being of a character adapted to oier less electrical resistance upon theapplication of increased pressure thereto, and `vice versa, an electric 4supply means in circuit with said electrical resistance means, means controlled by relative rock movement of said members for cutting in and out said supply means, and indicating means in circuit with said resistance means and said supply means and adapted to register current flow through said resistance means in terms of pressure ,applied to the work through said members and said resistance means.

6. A torque measuring wrench comprising a body member, a member rockably supported by said body member and having provision for opi erably engaging the work, opposed arm elements connected in circuit with both said electric resistance means, a current registering device in circuit with said current supply means and said electrical resistance means, and switch means associated with said members and operable by relative rock movement thereof to open or close the electric circuit through said supply means, said registering device and one or the other of said resistance means, dependent upon the direction of rock movement of said rock member.

7. A torque measuring wrench comprising a body member, amember rockably supported by said body member and having provision -for operative engagement with the work, arm elements on the opposite sides of the rock center of said rock member, carbon resistance stacks carried by said body member in alignment with said arm elements, pressure members between said carbon resistance stacks and said arm elements, electric current supply means in circuit with both of said carbon resistance stacks, current registering means in circuit with said supply means and both of said carbon resistance stacks, and switch means associated with said members and operated by said relative rock movement between said members to open or close the electric circuit through l said supply means, said registering device and one or the other of said carbon resistance stacks,

dependent upon the direction of rock movement of said rock member relative to said body member.

8. A torque measuring wrench comprising a body member, a member rockably supported by said body member and having provision for operable engagement with the work, arms on said rock member, an electrical resistance element carried by said body member and adapted to be operatively engaged by both of said arms to apply pressure thereto in a direction dependent upon the direction of rock movement of said rock member relative. to said body member, said electrical resistance means being of a character adapted to offer variable resistance to flow of electric current upon variation in pressure applied thereto, means in circuit with said electric o resistance means for supplying electric current thereto, and means in circuit with said supply means and said resistance means for registering the iiow of current through said resistance means in terms of pressure applied through said body member, said resistance means and said rockV member to the work. k

9. A torque measuring wrench comprising a body member, a member rockably supported thereby and having provision for operatively engaging the work, arm members on said rock member extending along said body member, a carbon resistancek stack carried by said body member at such a position that its opposite ends are aligned with said arms, pressure members between said arms and the opposite ends of said carbon resistance stack, electric supply means in circuit ywith said carbon resistance stack, and means for registering current ilow through said carbon resistance stackin terms of pressure applied through said body member, said stack and rock member tothe work.

10. A torque measuring wrench comprising a Cil gaging the work, arm members on said rock member and extending along said body member, a carbon resistance stack carried by said body member and disposed laterally between said arms, means operatively connecting each said arm with said carbon rsistance stack, electric current supply means in circuit with said carbon resistance stack, current registering means in circuit with said supply means and said carbon resistance stack andhaving a scale calibrated to indicate current flow in terms of pressure applied through the carbon resistance stack to the work, and switch means controlled by rock movement of said rock member for opening and closing the electric circuit through said supply means, said registering device and carbon resistance stack.

11. In a torque measuring wrench, a member having provision for operatively engaging the work, a second member through which pressure is applied to the wrench, electrical means disposed between said two members and controlled by relative movement of said members for measuring the amount of force or torque applied to the work, said electrical means including switch means adapted to be closed by relative movement'l of said two members for cutting in and out said electrical means so that the latter is eiective only when pressure is applied through the wrench to a piece of work.

HERMAN W. ZIMMERMAN. 

